This application describes a study of the morphological and physiological organization of the inner plexiform layer of a mammalian retina in which intracellular responses of the various types of neurons will be directly matched with their morphology and synaptology. The experimental approach include: 1) using the isolated rabbit retina eyecup preparation and intracellular recording techniques to examine the physiology of bipolar, amacrine and ganglion cells; 2) injecting horseradish peroxidase into the physiologically identified cell; 3) making a camera lucida drawing of the injected cell and obtaining a computer graphics reconstruction of its three dimensional geometry; 4) embedding and serial thin-sectioning the stained cell to examine with the electron microscope its connectivity. The study will center upon completing the analysis of the rod pathway through the inner plexiform layer. First, the relative contribution of rod and cone inputs into ganglion cells will be investigated by extracellular recordings with metal electrodes. Secondly, with the outer pipette of a coaxial microelectrode, rod dominated ganglion cells will be localized by extracellular recordings; they will be subsequently penetrated with the inner pipette to examine their intracellular activity and stain them with the ultrastructural tracer. Finally, their connectivity will be studied by three-dimensional computer graphics reconstruction from electron micrographs of serial thin sections. The functional interactions at the synapses between the various neurons inserted along the rod pathway will be investigated by intracellular recordings during the application of an on-channel blocking agent. Studies of this sort which directly correlate anatomy and physiology in a mammalian retina provide crucial information to understand the neuronal network which processes visual information in the human retina.